Display screen or portion thereof with an animated graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with an animated graphical user interface showing a first image of my new design;

FIG. 2 is a second image thereof; and,

FIG. 3 is a third image thereof.

The broken lines illustrate a display screen or portion thereof, and form no part of the claimed design. The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-3 . The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with an animated graphical user interface, as shown and described. 